Entering and exiting mechanisms on public transportation vehicles are known, in particular, in the form of passenger doors, entrance ramps, sliding steps or the like. Suitable driving devices are provided in order to move the respective entering and exiting mechanisms. These driving devices are frequently arranged in the region of the door frames or door portals above an opening and serve for opening and closing doors. Such doors in public transportation vehicles are typically realized in the form of swinging-sliding doors that also carry out a lateral displacement in addition to a swinging motion during opening and closing operations. Door systems of this type are known, for example, from EP 1 040 979 A2 and EP 1 314 626 A1. The driving devices for mere revolving or swinging doors that do not carry out a lateral displacement are usually also arranged above or underneath the doors in the region of the door portal. For example, DE 203 16 764 U1 describes the arrangement of a driving device in the upper region of a door portal.
It is furthermore known to realize driving devices of this type in a very compact fashion such that they can be integrated into the rotary column of a passenger door. Such a driving device is disclosed, for example, in DE 20 2008 007 585 U1. In addition to saving space, the accommodation of the drive unit directly in the rotary column provides numerous advantages with respect to the maintenance and installation of the entire driving device. Due to a special bearing arrangement, the driving device can furthermore remain largely unaffected by loads caused due to motions of the vehicle, the portal or the rotary column.
However, one frequent problem of such compact drive systems can be seen in that significant forces are exerted upon the drive unit and the gear via the lever arms of the door system when the door leaves are subjected to high forces in the open or closed state. Such high forces occur, in particular, during vandalism or opening and closing operations in overcrowded vehicles and can result in damages to the drive and/or the gear, in particular, if they are applied jerkily, e.g. on the door leaf.
In order to solve this problem, for example, WO 2011/067001 A1 proposes to provide a coupling device between the drive unit and a holding component, by means of which the driving device is arranged on the vehicle. Once a limiting value of the torque acting upon the drive unit is exceeded, the coupling device enables the drive unit to rotate about a vertical axis. This means that the entire drive unit also turns once a certain torque is exceeded such that damages to the driving motor and the gear are prevented. However, the coupling device only disengages when a certain limiting value is exceeded whereas the torques required for the normal operation can be transmitted without problems. In addition, a bearing is provided between the coupling device and the holding component and allows a wobbling motion of the rotary column with the coupling device in order to thusly compensate distortions and excursions of the rotary column due to motions of the vehicle.
In order to prevent doors from being manually opened, self-locking step-down gears may be utilized in order to block the doors. However, it has been proposed, for example in WO 2009/060085 A1, to forgo the utilization of a self-locking step-down gear such that the doors of the vehicle can be manually moved without blocking this motion due to the self-locking effect of the gear. A separate blocking device is provided such that the doors can still be prevented from being inadvertently opened. However, the blocking device can be controlled in order to open the doors in case of an emergency, i.e. the blocking effect of the blocking device can be canceled, if so required. Due to the low self-locking effect of the gear, the option of manually actuating the entering and exiting mechanisms is always ensured in case of an emergency, wherein it is merely required to cancel the blocking effect of the blocking device.